1. Motion, Speed, and Velocity
Physics
Motion, Speed, and Velocity

2. SC Standards Covered PS-5.1 PS – 5.2 PS – 5.6
Explain the relationship among distance, time, direction, and the velocity of an object
PS – 5.2
Use the formula v=d/t to solve problems related to average speed or velocity
PS – 5.6
Represent linear motion of objects on distance – time graphs

3. Motion When an object changes its position, motion has occurred.
Distance- How far an object has moved.
Displacement- How far an object has moved in relation to its starting point.
Consider direction
Example: Two runners travel along the same straight path in a straight line for 500 meters. At the end of the run their distances are the same but their displacements are different. How can this be so?

4. Speed- Distance an object travels per unit of time
Relationships between speed, distance, and time:
Speed = Distance/ Time = d/ t
Constant Speed- speed does not change over time
Average Speed- speed of motion when speed is changing
Avg Speed = Total Distance/ Total Time
Instantaneous Speed- speed at any given moment in time (speedometer)

5. Speed
The units for speed:
meters/second (m/sec)
kilometers/hour (km/hr)
Speed that does not change is constant speed

6. Graphing Motion Graph distance on the y-axis and time on the x-axis
Slope = rise = distance = speed
run time

7. Distance - Time Graph
If something is not moving, a horizontal line is drawn.
If something starts out slow and then speeds up, its change in speed can look like this.

8. Learning Checkpoint This graph shows several stages of motion:
Stage 1: 100 m in 10 s
Stage 2: 50 m in 10 s
Stage 3: 150 m in 20 s
Calculate the speed as indicated by each of the colors.
Calculate the average speed.
What is the total distance?
What is the displacement?

9. Solution Stage 1: S= d/ t 100 m/ 10 s= 10 m/s Stage 2: S= d/t
Ave Speed= Tot d/ Tot t
300 m/ 40 s= 7.5 m/s
Distance = 300 meters
Displacement = 0 meters

10. Velocity The speed and direction of an object’s motion.
88 km / hr southwest

11. Acceleration
The change in velocity
Acceleration is measured in m/sec/sec or m/sec2
Formula is:
(final velocity - original velocity)/time

12. Deceleration vs. Acceleration
A decrease in velocity is deceleration or negative acceleration
A distance-time graph for acceleration is always a curve

13. Centripetal Acceleration
Acceleration directed toward the center of circular path

14. Frames of Reference
The object or point from which movement is determined
Movement is relative to an object that appears stationary
Earth is the most common frame of reference